Question 4.61: The OP AMP in Figure P4-61 operates as a comparator. Find th......
The OP AMP in Figure P4-61 operates as a comparator. Find the output voltage when v_S = 2 V.
Repeat for v_S = ! 2 V and v_S = 6 V.
The circuit is connected such that the voltage at the negative input terminal is always 5 V and the voltage at the positive input terminal is v_S. In this case, the ideal OP AMP assumptions do not apply and we must use the fundamental OP AMP equation, v_O = A(v_P – v_N), and our knowledge of OP AMP saturation to determine the output voltages. For this circuit, +v_{CC} = 15 V and -v_{CC} = 0 V. We still assume the OP AMP’s open-loop gain, A, is very large. When v_P > v_N, the OP AMP will try to produce a positive output voltage with a large magnitude and will saturate at its maximum output value, 15 V. When v_P < v_N, the OP AMP will try to produce a negative output voltage with a large magnitude and will saturate at its minimum output value, 0 V.
Answer:
The following table summarizes the results described above.
| v_S (V) | v_O (V) |
| 2 | 0 |
| -2 | 0 |
| 6 | 15 |